/* J. David's webserver */
/* This is a simple webserver.
 * Created November 1999 by J. David Blackstone.
 * CSE 4344 (Network concepts), Prof. Zeigler
 * University of Texas at Arlington
 *
 * This program compiles for Sparc Solaris 2.6.
 * To compile for Linux:
 *   1) Comment out the #include <pthread.h> line.
 *   2) Comment out the line that defines the variable worker_thread.
 *   3) Comment out the two lines that run pthread_create().
 *   4) Uncomment the line that runs accept_request().
 *   5) Remove -lsocket from the Makefile.
 */
#include <stdio.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <ctype.h>
#include <strings.h>
#include <string.h>
#include <sys/stat.h>
#include <pthread.h>
#include <sys/wait.h>
#include <stdlib.h>
#include <stdint.h>
#include <time.h>

#define ISSPACE(x) isspace((int)(x))

#define SERVER_STRING "Server: TinyHttpd/0.1.0\r\n"
#define STDIN   0
#define STDOUT  1
#define STDERR  2


void accept_request(void *);
void bad_request(int);
void cat_file(int, FILE *);
void cannot_execute(int);
void error_die(const char *);
void execute_shell(int, const char *, const char *, const char *);
int  get_line(int, char *, int);
void write_headers(int);
void not_found(int);
void serve_file(int, const char *);
void get_time_str(char *);
void write_log(const char *);
int  str_case_eq(const char *, const char *);
int  startup(u_short *);
void unimplemented(int);


/**********************************************************************/
/* A request has caused a call to accept() on the server port to
 * return.  Process the request appropriately.
 * Parameters: the socket connected to the client */
/**********************************************************************/
void accept_request(void *arg) {
    int client = (intptr_t) arg;
    char buf[1024];
    size_t numchars;
    char method[255];
    char url[255];
    char path[512];
    char log_msg[2048];
    size_t i, j;
    struct stat st;

    int is_cgi = 0;

    char *query_string = NULL;

    numchars = get_line(client, buf, sizeof(buf));

    if (numchars > 0) {
        sprintf(log_msg, "client_requst::%s, length:[%zu]\n", buf, numchars);

        write_log(log_msg);

        i = 0; j = 0;

        while (!ISSPACE(buf[i]) && (i < sizeof(method) - 1)) {
            method[i] = buf[i];
            i++;
        }

        j=i;

        method[i] = '\0';

        if (!str_case_eq(method, "GET") && !str_case_eq(method, "POST")) {
            unimplemented(client);
            return;
        }

        if (str_case_eq(method, "POST")) {
            is_cgi = 1;
        }

        i = 0;
        while (ISSPACE(buf[j]) && (j < numchars)){
            j++;
        }

        while (!ISSPACE(buf[j]) && (i < sizeof(url) - 1) && (j < numchars)) {
            url[i] = buf[j];
            i++; j++;
        }

        url[i] = '\0';

        if (str_case_eq(method, "GET")) {
            query_string = url;

            while ((*query_string != '?') && (*query_string != '\0')) {
                query_string++;
            }

            if (*query_string == '?') {
                is_cgi = 1;

                *query_string = '\0';
                query_string++;
            }
        }

        sprintf(path, "htdocs%s", url);

        if (path[strlen(path) - 1] == '/') {
            strcat(path, "index.html");
        }

        if (stat(path, &st) == -1) {
            while ((numchars > 0) && strcmp("\n", buf))  /* read & discard headers */
                numchars = get_line(client, buf, sizeof(buf));
            not_found(client);
        } else {
            if ((st.st_mode & S_IFMT) == S_IFDIR) {
                strcat(path, "/index.html");
            }

            if ((st.st_mode & S_IXUSR) || (st.st_mode & S_IXGRP) || (st.st_mode & S_IXOTH)) {
                is_cgi = 1;
            }

            if (is_cgi) {
                execute_shell(client, path, method, query_string);
            } else {
                serve_file(client, path);
            }
        }
    }

    close(client);
}

/**********************************************************************/
/* Inform the client that a request it has made has a problem.
 * Parameters: client socket */
/**********************************************************************/
void bad_request(int client) {
    char buf[1024];

    sprintf(buf, "HTTP/1.0 400 BAD REQUEST\r\n");
    send(client, buf, sizeof(buf), 0);
    sprintf(buf, "Content-type: text/html\r\n");
    send(client, buf, sizeof(buf), 0);
    sprintf(buf, "\r\n");
    send(client, buf, sizeof(buf), 0);
    sprintf(buf, "<P>Your browser sent a bad request, ");
    send(client, buf, sizeof(buf), 0);
    sprintf(buf, "such as a POST without a Content-Length.\r\n");
    send(client, buf, sizeof(buf), 0);
}

/**********************************************************************/
/* Put the entire contents of a file out on a socket.  This function
 * is named after the UNIX "cat" command, because it might have been
 * easier just to do something like pipe, fork, and exec("cat").
 * Parameters: the client socket descriptor
 *             FILE pointer for the file to cat */
/**********************************************************************/
void cat_file (int client, FILE *resource) {
    char buf[1024];

    fgets(buf, sizeof(buf), resource);

    while (!feof(resource)) {
        send(client, buf, strlen(buf), 0);
        fgets(buf, sizeof(buf), resource);
    }
}

/**********************************************************************/
/* Inform the client that a CGI script could not be executed.
 * Parameter: the client socket descriptor. */
/**********************************************************************/
void cannot_execute(int client) {
    char buf[1024];

    sprintf(buf, "HTTP/1.0 500 Internal Server Error\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "Content-type: text/html\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "<P>Error prohibited CGI execution.\r\n");
    send(client, buf, strlen(buf), 0);
}

/**********************************************************************/
/* Print out an error message with perror() (for system errors; based
 * on value of errno, which indicates system call errors) and exit the
 * program indicating an error. */
/**********************************************************************/
void error_die(const char *sc) {
    perror(sc);
    exit(1);
}

/**********************************************************************/
/* Execute a Shell script. */
/**********************************************************************/
void execute_shell (int client, const char *path, const char *method, const char *query_string) {
    FILE *fp;

    char c;
    char headers[256];
    char output[1024];
    char log_msg[2048];

    headers[0] = 'A';
    headers[1] = '\0';

    int numchars = 1;
    int content_length = -1;

    if (str_case_eq(method, "GET")) { /*GET*/
        while ((numchars > 0) && strcmp("\n", headers)) { /* read & discard headers */
            numchars = get_line(client, headers, sizeof(headers));
        }
    } else if (str_case_eq(method, "POST")) { /*POST*/
        numchars = get_line(client, headers, sizeof(headers));

        while ((numchars > 0) && strcmp("\n", headers)) {
            headers[15] = '\0';

            if (str_case_eq(headers, "Content-Length:")) {
                content_length = atoi(&(headers[16]));
            }

            numchars = get_line(client, headers, sizeof(headers));
        }

        if (content_length == -1) {
            bad_request(client);
            return;
        }
    } else { /*HEAD or other*/

    }
 
    fp = popen("htdocs/color.cgi", "r");

    fgets(output, sizeof(output), fp);

    sprintf(log_msg, "execute_shell_result:: %s", output);

    write_log(log_msg);

    // write headers
    write_headers(client);

    if (str_case_eq(method, "POST")) {
        for (int i = 0; i < content_length; i++) {
            recv(client, &c, 1, 0);
        }
    }

    // send body
    send(client, output, strlen(output), 0);

    pclose(fp);
}

/**********************************************************************/
/* Get a line from a socket, whether the line ends in a newline,
 * carriage return, or a CRLF combination.  Terminates the string read
 * with a null character.  If no newline indicator is found before the
 * end of the buffer, the string is terminated with a null.  If any of
 * the above three line terminators is read, the last character of the
 * string will be a linefeed and the string will be terminated with a
 * null character.
 * Parameters: the socket descriptor
 *             the buffer to save the data in
 *             the size of the buffer
 * Returns: the number of bytes stored (excluding null) */
/**********************************************************************/
int get_line(int sock, char *buf, int size) {
    int i = 0;
    char c = '\0';
    int n;

    while ((i < size - 1) && (c != '\n')) {
        n = recv(sock, &c, 1, 0);
        /* DEBUG printf("%02X\n", c); */
        if (n > 0) {
            if (c == '\r') {
                n = recv(sock, &c, 1, MSG_PEEK);
                /* DEBUG printf("%02X\n", c); */
                if ((n > 0) && (c == '\n'))
                    recv(sock, &c, 1, 0);
                else
                    c = '\n';
            }
            buf[i] = c;
            i++;
        } else if (n <= 0) {
            return 0;
        }
    }

    buf[i] = '\0';

    return i;
}

/**********************************************************************/
/* Return the informational HTTP headers about a file. */
/* Parameters: the socket to print the headers on
 *             the name of the file */
/**********************************************************************/
void write_headers (int client) {
    char buf[1024];

    strcpy(buf, "HTTP/1.0 200 OK\r\n");
    send(client, buf, strlen(buf), 0);
    strcpy(buf, SERVER_STRING);
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "Content-Type: text/html\r\n");
    send(client, buf, strlen(buf), 0);
    strcpy(buf, "\r\n");
    send(client, buf, strlen(buf), 0);
}

/**********************************************************************/
/* Give a client a 404 not found status message. */
/**********************************************************************/
void not_found(int client) {
    char buf[1024];

    sprintf(buf, "HTTP/1.0 404 NOT FOUND\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, SERVER_STRING);
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "Content-Type: text/html\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "<HTML><TITLE>Not Found</TITLE>\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "<BODY><P>The server could not fulfill\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "your request because the resource specified\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "is unavailable or nonexistent.\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "</BODY></HTML>\r\n");
    send(client, buf, strlen(buf), 0);
}

/**********************************************************************/
/* Send a regular file to the client.  Use headers, and report
 * errors to client if they occur.
 * Parameters: a pointer to a file structure produced from the socket
 *              file descriptor
 *             the name of the file to serve */
/**********************************************************************/
void serve_file (int client, const char *filename) {
    FILE *resource = NULL;
    int numchars = 1;
    char buf[1024];

    buf[0] = 'A';
    buf[1] = '\0';

    while ((numchars > 0) && strcmp("\n", buf)) { /* read & discard headers */
        numchars = get_line(client, buf, sizeof(buf));
    }

    resource = fopen(filename, "r");

    if (resource == NULL) {
        not_found(client);
    } else {
        write_headers(client);
        cat_file(client, resource);
    }

    fclose(resource);
}

void get_time_str(char *time_str) {
    time_t rawtime;
    struct tm *tminfo;

    time(&rawtime);
    tminfo = localtime(&rawtime);

    sprintf(time_str, "%d/%d/%d %02d:%02d:%02d", tminfo->tm_year + 1900, tminfo->tm_mon + 1, tminfo->tm_mday, tminfo->tm_hour, tminfo->tm_min, tminfo->tm_sec);
}

/**********************************************************************/
/* Write a log message to file */
/**********************************************************************/
void write_log (const char *msg) {
    FILE *resource = NULL;

    char time_str[48];

    // get time string
    get_time_str(time_str);

    // open log file
    resource = fopen("logs/httpd.log", "a");

    if (resource != NULL) {
        fprintf(resource, "%s %s", time_str, msg);
    }

    fclose(resource);
}

/**********************************************************************/
/* compare string */
/**********************************************************************/
int str_case_eq (const char *str1, const char *str2) {
    return strcasecmp(str1, str2) == 0 ? 1 : 0;
}

/**********************************************************************/
/* This function starts the process of listening for web connections
 * on a specified port.  If the port is 0, then dynamically allocate a
 * port and modify the original port variable to reflect the actual
 * port.
 * Parameters: pointer to variable containing the port to connect on
 * Returns: the socket */
/**********************************************************************/
int startup(u_short *port) {
    int httpd_sock = 0;
    int on = 1;
    struct sockaddr_in server_addr;

    httpd_sock = socket(PF_INET, SOCK_STREAM, 0);

    if (httpd_sock == -1) {
        error_die("socket");
    }

    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(*port);
    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);

    if ((setsockopt(httpd_sock, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on))) < 0) {  
        error_die("setsockopt failed");
    }

    if (bind(httpd_sock, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) {
        error_die("bind");
    }

    if (*port == 0) { /* if dynamically allocating a port */
        socklen_t server_addr_len = sizeof(server_addr);

        if (getsockname(httpd_sock, (struct sockaddr *)&server_addr, &server_addr_len) == -1){
            error_die("getsockserver_addr");
        }

        *port = ntohs(server_addr.sin_port);
    }

    if (listen(httpd_sock, 5) < 0) {
        error_die("listen");
    }

    return(httpd_sock);
}

/**********************************************************************/
/* Inform the client that the requested web method has not been
 * implemented.
 * Parameter: the client socket */
/**********************************************************************/
void unimplemented(int client) {
    char buf[1024];

    sprintf(buf, "HTTP/1.0 501 Method Not Implemented\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, SERVER_STRING);
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "Content-Type: text/html\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "<HTML><HEAD><TITLE>Method Not Implemented\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "</TITLE></HEAD>\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "<BODY><P>HTTP request method not supported.\r\n");
    send(client, buf, strlen(buf), 0);
    sprintf(buf, "</BODY></HTML>\r\n");
    send(client, buf, strlen(buf), 0);
}

/**********************************************************************/

int main(void) {
    int server_sock = -1;
    u_short port = 4000;
    int client_sock = -1;
    struct sockaddr_in client_addr;
    socklen_t  client_addr_len = sizeof(client_addr);
    pthread_t worker_thread;

    server_sock = startup(&port);
    printf("httpd listen on port %d\n", port);

    while (1) {
        client_sock = accept(server_sock, (struct sockaddr *) &client_addr, &client_addr_len);

        if (client_sock == -1) {
            error_die("accept");
        }

        // start a thread to handle the request
        if (pthread_create(&worker_thread , NULL, (void *) accept_request, (void *)(intptr_t) client_sock) != 0) {
            perror("pthread_create");
        }
    }

    close(server_sock);

    return(0);
}
